Suggestions for observing the total eclipse of the sun on January 1, 1889

SUGGESTIONS

FOR OBSERVING THE

TOTAL ECLIPSE OF THE SUN

ON

JANUARY 1, 1889.

BY

EDWARD S. JiOLDEN, LL.D.,

Director of the Lick Observatory.

PRINTED BY AUTHORITY OF THE REGENTS OF THE UNIVERSITY
OF CALIFORNIA. .

SACRAMENTO:

STATE OFFICE, : : : : J. D. YOUNG, SUPT. STATE PRINTING.
1888.

FT

27 1G33

I

SUGGESTIONS

FOR OBSERVING THE

TOTAL ECLIPSE OF THE SUN

ON

JANUARY 1, 1889,

BY

EDWARD S. HOLDEN, LL.D.,

Director of the Eick Observatory.

PRINTED BY AUTHORITY OF THE REGENTS OF THE UNIVERSITY
OF CALIFORNIA.

SACRAMENTO:

STATE OFFICE, : : : : J. D. YOUNG, SUPT. STATE PRINTING.
1888.

INTRODUCTORY NOTE.

The following brief suggestions in regard to observing the
total solar eclipse of January I, 1889, have been compiled
from various sources, in the belief that they may be of use to
intending observers.

It is hoped that the Lick Observatory may find means to
print the results of observations made by its astronomers in the
field, and at Mount Hamilton. Any valuable observations
made by other observers, and promptly communicated to the
Observatory, will be included in such a publication. Corre-
spondence on this and other subjects relating to the eclipse
should be addressed to the Director of the Lick Observatory,
Mount Hamilton, San Jose, California.

1888, September 17.

SUGGESTIONS TO OBSERVERS.

PHENOMENA OF TOTAL ECLIPSES. — The beginning of a
total solar eclipse is marked simply by the small black notch
made in the luminous disc of the sun by the advancing edge
or limb of the moon. This always occurs on the western half
of the sun, as the moon moves from west to east in its orbit.
An hour or more must elapse before the moon has advanced
sufficiently far in its orbit to cover the sun's disc. During this
time the disc of the sun is gradually hidden until it becomes
a thin crescent.

The actual amount of the sun's light may be diminished to
two thirds or three fourths of its ordinary amount without its
being strikingly perceptible to the eye. What is first noticed
is the change which takes place in the color of the surrounding
landscape, which begins to wear a ruddy aspect. This grows
more and more pronounced, and gives to the adjacent country
that weird effect which lends so much to the impressiveness of
a total eclipse. The color changes because the sun's atmos-
phere absorbs a larger proportion of the blue rays than of the
red. As this absorption is dependent on the thickness of the
solar atmosphere through which the rays must pass, it is plain
that just before the sun is totally covered, the rays by which
we see it will be redder than ordinary sunlight, since they
come from points near the sun's limb and must pass through
the greatest thickness of the sun's atmosphere.

The color of the light becomes more and more lurid up to
the moment when the sun has nearly disappeared. If the
spectator is upon the top of a high mountain, he can then
begin to see the moon's shadow rushing towards him at the
rate of about a mile in a second. Just as the shadow reaches

851037

4 Suggestions for Observing

him there is a sudden increase of darkness; the brighter stars
begin to shine in the dark lurid sky, the thin crescent of the
sun breaks up into small points or dots of light, which sud-
denly disappear, and the moon itself, an intensely black ball,
appears to hang isolated in the heavens.

An instant afterward the sun's corona is seen surrounding the
black disc of the moon with a soft effulgence quite different
from any other light known to us. Near the moon's limb it is
intensely bright, and to the naked eye uniform in structure;
5' or 10' from the limb this inner corona has a boundary more
or less defined, and from this extend streamers and wings of
fainter and more nebulous light. These are of various shapes,
sizes, and brilliancy. No two solar eclipses yet observed have
been alike in this respect. These appearances, though change-
able, do not appear to change in the time the moon's shadow
requires to pass from the first contact with the earth to its last.

Superposed upon these wings may be seen (sometimes with
the naked eye) the red flames, or protuberances, which were
first discovered during a total eclipse. These need not be
more closely described here, as they can now be studied at
any time by the aid of a spectroscope.

The total phase of a solar eclipse lasts for a few minutes
(never more than six or seven, and about two minutes only at
the eclipse of January i, 1889), and during this time, as the
eye becomes more and more accustomed to the faint light, the
outer corona is seen to stretch further and further away from
the sun's limb. At the eclipse of 1878, July 29, it was seen
to extend more than 6° (about 9,000,000 miles) from the sun's
limb. Just before the end of the total phase there is a sudden
increase of the brightness of the sky, due to the increased
illumination of the earth's atmosphere near the observer, and
in a moment more the sun's rays are again visible, seemingly
as bright as ever. From the end of totality till the last con-
tact the phenomena of the first half of the eclipse are repeated
in inverse order.

The Eclipse of January 1, 1889.

TELESCOPIC APPEARANCE OF THE CORONA. — Such are the
appearances to the naked eye. The corona, as seen through
the telescope, is, however, of a very complicated structure.
The inner corona is usually composed of bright striae or fila-
ments separated by darker bands, and some of these latter
are occasionally seen to be almost totally black. The appear-
ances are extremely irregular, but they are often as if the
inner corona were made up of brushes of light on a darker
background.

The corona and red prominences are solar appendages.

It was formerly doubtful whether the corona was an atmos-
phere belonging to the sun or the moon. At the eclipse of
1860 it was proved by measurements that the red prominences
belonged to the sun and not to the moon, since the moon
gradually covered them by its motion, they remaining attached
to the sun. The corona has also since been .shown to be a
solar appendage.

LICK OBSERVATORY TIME-SIGNALS.

On the 29th, 3Oth, and 3ist of December, and on the ist
and 2d of January, the time-signals of the Lick Observatory
will be sent to (nearly) every railway station in California auto-
matically from a standard mean-time clock. Observers should
compare their watches with the beats of the sounder at noon
in the nearest railway station, when possible. These signals
will be similar to the regular noon Time-Signals of this Observ-
atory, which furnishes the official time to the Southern Pacific
Company. These signals commence with a warning "rattle"
between 11:56 and 11:57 °f Pacific Standard Time, there is
then a pause of one minute (during which the wires are cleared
for the transmission of the "noon-signal"), and the first beat
of the clock, which will be heard at the distant telegraph sta-
tion is 1 1 hr. 58 min. oo sec. of P. S. T. Thereafter, the clock
will beat every even second — leaving out the 58th second — the
first beat after this short pause is 11:59:0, and the clock will

Suggestions for Observing

continue to beat the even seconds until 11:59:50, when there
will be a pause of 10 seconds, and the last beat heard will be
12:00:00, or NOON of Pacific Standard Time (equal to 8:00:00
of Greenwich Mean Time).

If it is not practicable to visit one of the railway telegraph
stations at noon, for these signals, the beats of the Lick Observ-
atory clock may be heard by telephone at any time of the day,
following out the programme given below.

To hear the beats of the Lick Observatory Standard Clock,
call the Central Office, and ask that the San Jose operator
put on the Lick Observatory clock signal. When this rs done,
the beats of the Lick Observatory clock will be heard every
two seconds. At the end of every minute the 58th second is
omitted. At the end of every 5th minute (o, 5, 10, 15, 20, 25,
30, 35, 40, 45, 50, 55, 60) the 52d, 54th, 56th, and 58th seconds
are omitted.

To set your watch right : Get the beats of the Lick Observ-
atory clock in your telephone, and hold your watch where you
can see the second hand; listen to the beats, which are heard
every two seconds, until a pause of more than two seconds
comes; the first dot after such a pause begins some minute.
If the pause is ten seconds long, the minute is one of the num-
bered minutes of your watch-dial.

APPROXIMATE TIMES OF BEGINNING AND ENDING OF THE
TOTAL PHASE.

I have asked Professor SCHAEBERLE, of the Lick Observ-
atory, to compute the approximate Pacific Standard Times
of the beginning and ending of the total phase, and his results
are exhibited in the following table. They will serve a useful
purpose in enabling intending observers to select a suitable
station. The latitudes and longitudes of the various stations
were taken from a tracing of WHITNEY'S map of California,
made by Mr. HlLL, of this Observatory (a copy of a part of
which accompanies this pamphlet), and these positions may

The Eclipse of January 1, 1889.

7

be erroneous by considerable amounts on account of errors in
the map. Hence the computed times are merely approximate.

PLACE.

Total Eclipse.

Dura-
tion.

Begins.

Ends.

Mendocino ....

h

m. s.

45 3i

45 2
44 59
46 44

46 31
46 48
48 15
47 4i
47 46
47 43
47 56
47 52
47 59
48 10
48 02
48 23
48 19
48 32
49 13
49 17
48 59
50 25
50 43
49 53

50 21
SO 24

47 14
47 5
47 i
48 32
48 33
48 51
48 52
49 40

49 49
49 33
49 58
49 24
49 12
50 5
49 16
5° 17
5° 16
50 35
50 54
50 55
5i i
5i 47

52 12

5i 53
52 16
51 50

D

]

2

C
]
1
]

1. 8.

43
- 03

\ 02
48
\ 02
5 03

> 37
[ 59
i 03

[ 50

I 02
[ 32
[ 13

[ 55
H
54
57
03
4i
38
02

22

29
OO

55
26

Punta Arenas ....

Ukiah

Cloverdale

Lakeport . . ....

Lick Observatory Station

Calistoga ... .

Willows

Norman

Orland

Maxwell ... ....

Corning

Tehama

Colusa Junction

Sesma

Colusa

Chico

Nelson

Yuba

Marysville

Oroville ...

Grass Valley

Nevada City

Ouincy

Dow n ieville

Susan ville

Approximate times of First and Last Contacts. (Pacific
Standard Time.)

1st Contact.

4th Contact.

At the Lick Observatory

nh

24™ 58s

•2h Qm •26s

At Professor Davidson's Observatory, San

Francisco

0

23 8

3 8 56

At the Students' Observatory, Berkeley ....

0

23 31

398

At the Lick Observatory field station

0

22 19

3 7 17

The point of first contact will be about 91° from the north point of the sun's
limb measured towards the west.

NOTE. — In telescopic observations of the first contact, care should be taken to
employ an eye-piece with a field of view of at least 1 5' to 20' of arc. The second
and third contacts should be observed with high powers and small fields ; and the
fourth contact may be so observed, though it is probably better to employ the same
eye-piece for observations of both the first and fourth contacts.

8 Suggestions for Observing

GENERAL REMARKS.

The phenomena of a total eclipse are so various, so start-
ling, so impressive, and so indescribably novel and fascinating
that those engaged in observation will do well to confine their
attention to that special portion which they can best observe,
leaving the other portions to other members of the party.
Only in this way can a definite result be certainly attained.

During the observation of an eclipse, it is necessary that
quiet and stillness should be maintained. A whispering, mur-
muring crowd, much more a noisy, talkative one, may seri-
ously impair observations, or even occasion their total loss.
What can be seen with the unaided eye can be as well seen
many miles away as in the immediate vicinity of those who
are provided with instruments for precise observations. No
visitors will be admitted to the Lick Observatory on the day of
the eclipse.

The nature and character of the instruments employed
should be stated by each observer in his report, together with
any circumstance which may affect the reliability or value of
the results. Thus, in the case of a telescope, the aperture
used, focal length and magnifying power, and the shade-glasses
employed, should be recorded; also, during the observations,
the transition of the eye of the observer from light to obscurity,
or the reverse, the deposit of dew on the glasses, or any change
or defect in adjustment. Notes at the time should be brief
and condensed, but written out at length immediately after-
wards, and without conference with others. The results of
such a conference should be given separately.

CHOICE OF OBSERVING STATION.

A position should be selected which is free from the annoy-
ances of wind, dust, and dazzling reflection from water, and
the noise and din of a thoroughfare; which affords a clear
view of the portion of the heavens to which the attention will

The Eclipse of January 1, 1889. 9

be directed, and an unobstructed meridian, if precise observa-
tions for time are contemplated ; and elevated above the ordi-
nary range of fogs, where fogs are to be apprehended.

The place should be noted and described, and its bearing
and distance from some public building or prominent land-
mark should be determined. It should be resorted to one or
more days in advance, in order to have everything in readiness
and suitably arranged.

I. OBSERVATIONS OF THE CONTACTS.

These consist in observing the instants of beginning and
end both of the eclipse and of the total phase, together with
the positions of the points of contact, and serve to give a pre-
cise determination of the moon's place.

It is desirable that the beginning and end of the eclipse
should be carefully observed at all fixed observatories within
its limits. The beginning and end of the total phase can only
be observed within the belt of totality.

The value of such observations depends on the precision
with which the instant of contact is appreciated and its time
recorded, and the exactness with which the correction of the
chronometer and the longitude and latitude of the place are
determined. Where good observations have been made, meas-
ures may be taken subsequently for fixing the geographical
position.

II. OBSERVATIONS NEAR THE LIMITS OF THE

SHADOW.

The intelligent inhabitants of towns near the edge of the
belt 'of totality may furnish observations by which the limits
can be accurately determined by simply noting how many sec-
onds the sun is wholly obscured by the moon. The following
directions for doing this are mostly taken from a circular issued
by the Naval Observatory asking for observations of the eclipse
of August 7, 1869.

10 Suggestions for Observing

INSTRUMENTS: The only indispensable instrument is a
good watch, provided with a seconds-hand, and having a
white face. It may be well to provide a lighted lantern for
use in case of necessity. The minute-hand of the watch should
be carefully set so as to be on the exact minute when the sec-
onds-hand is at 6os. This being done it is no matter how far
wrong the watch may be.

A good auxiliary will be a common spy-glass lashed to a
round post so as to be steady enough to give an easy view of
the sun. To lessen the brilliancy of the sun, cover the object
glass with a pasteboard, tin, or wooden cap having a round hole
three fourths of an inch in diameter cut in its center.

The spy-glass will be worse than useless unless one is accus-
tomed to its use, and has it fastened so as to be steady.

An opera-glass held in the hand may also serve a good pur-
pose. A smoked glass should also be prepared, but one part
of the glass should be smoked very lightly so that it can be
used should the day be cloudy.

Arrangement for Observation. — Each observation should be
made by a party of three persons. Only one instrument of
each kind — watch, glass, etc. — is needed by a party. A station
should be selected where they will be free from all interruption,
either in the open air or at an open window, facing south or
southwest. Be sure that the sun can be seen from your station
at 1 130 P.M., by a trial one or two days before the eclipse. One,
at least, of the party must have a pencil and note book at hand
to record the time.

Tlie Observation. — When the visible part of the sun is reduced
to the narrowest crescent, the holder of the watch, keeping his
eye on the face, will begin to count the seconds aloud ; the
holder of the smoked glass, with or without the spy-glass, will
watch for the last ray of true sunlight, being careful to look
through the brightest part of the glass the eye will bear with-
out inconvenience; and the third observer, if there be one, will
look for the disappearance of sunlight with the naked eye, and
stand ready with pencil and paper to record the time. When

The Eclipse of January 1, 1889. 11

the last ray of the sun has disappeared, the observer with the
glass will call "time," and the exact second at which the call
was given must be immediately written down. The minute
also must be carefully noted and immediately recorded. It is
best to record the seconds first, and then the minutes. The
observers will then await the return of sunlight, the count of
seconds being kept up. The first flash of true sunlight will
seem to burst out suddenly, and the minute and second of its
appearance must be immediately recorded with the same care
as the time of disappearance. The difference of the two times
gives the duration of totality.

Valuable observations of the duration of totality can be made
at any points at or near the limits of the line of totality, in par-
ticular at or near the points named below. Observers should
remember that the fact that the eclipse was not total at their
stations is just as important as the other fact that the duration
of totality was one, two, or three seconds. If these observations
are carefully made, and promptly communicated to the Lick
Observatory, they will serve a useful purpose.

Northern Limit.

Westport, Mendocino County.
Kibesilla, Mendocino County.
Tilly, Mendocino County.
Cahto, Mendocino County.
Laytonville, Mendocino County.
Covelo, Mendocino County.
Camp Wright, Mendocino County.
Red Bluff, Tehama County.
Lyonsville, Tehama County.

Southern Limit.

Duncan's Mills, Sonoma County.
Occidental, Sonoma County.
Windsor, Sonoma County.
Mark West, Sonoma County.

12. Suggestions for Observing

America, Sonoma County.
Calistoga, Napa County.
Pope Valley, Napa County.
Brooks, Yolo County.
Capay, Yolo County.
Dunnigan, Yolo County.
Black's, Yolo County.
Grafton, Yolo County.
Wheatland, Yuba County.
Spencerville, Nevada County.
You Bet, Nevada County.
Lowell Hill, Nevada County.
Donner, Nevada County.
Alta, Placer County.
Dutch Flat, Placer County.
Gold Run, Placer County.
Blue Canyon, Placer County.
Emigrant Gap, Placer County.
Cisco, Placer County.

Special Precautions. — In appreciating the beginning of total-
ity there is danger of error from two sources. The first is that
the sun's crescent may become so narrow as to become invisi-
ble through the smoked glass, if this be too dark, several sec-
onds before it is really all covered, and thus the observer may
call the "time" too soon. Such a mistake may be detected
and corrected by the third observer looking on with the naked
eye, if the following circumstances be attended to:

The beginning of total eclipse is marked by a very rapid
increase of the darkness, caused by the advent of the moon's
shadow. If, then, the darkness increases more rapidly after
time is called than it did before, time was called too soon, and
must be repeated. The other danger is of the opposite kind,
and should be equally avoided. It is that the light of the
brilliant rose-colored protuberances which surround the dark
body of the moon during the total eclipse may be mistaken

The Eclipse of January 1, 1889. 13

for sunlight, and thus the critical moment be suffered to pass.
In this case each observer must determine separately the
exact second at which it ceased to grow darker, and if they
agree within one or two seconds, the time may be supposed
correct, and each one's estimate may be written down sepa-
rately. The observer with the smoked glass will be most
liable to the first of these mistakes; the naked-eye observer to
the last.

The return of sunlight will also be preceded by a reddish
glow on the border of the dark moon, which must not be mis-
taken for the sun. Indeed, if the observer be near the edge
of the shadow, it is probable that this red glow, which comes
from the hydrogen atmosphere of the sun, may be visible dur-
ing the whole time of totality.

All the recorded times, with an estimate of the uncertainties
to which the observers think they are liable, and a statement
of the place where made, giving distance in miles and direc-
tion from the Court House, if it be a county town, and from
the railroad station, if a railroad pass through, referring also to
the United States land surveys, should be immediately certi-
fied by the signatures of all three observers, and forwarded to
the Lick Observatory.

It is particularly requested that each party send off its report
before comparing notes with any other party; also, that the
original pencil record, however imperfect, accompany the re-
port; and it is hoped that many persons will take the pains to
make these simple yet valuable observations.

III. SPECTROSCOPIC OBSERVATIONS.

These are of special importance during the total phase. A
direct-vision spectroscope, attached to a telescope of moderate
power, is recommended as most convenient and most readily
manipulated. Familiarity with the most prominent lines of
the solar spectrum is an essential preparation. An assistant
should be trained to direct the telescope by the finder. The

14 Suggestions fcr Observing

spectra of various portions of the corona deserve careful exam
ination. The position of the part examined, and the time,
should be noted. Where there are several observers, it will be
better for each to confine his attention to a designated portion
rather than to attempt to observe the whole.

IV. METEOROLOGICAL OBSERVATIONS.

These include the ordinary record of the barometer, dry
and wet bulb thermometers, winds, clouds, and other condi-
tions of the atmosphere. Near, and during the total phase,
the changes of the thermometer and hygrometer, formation of
clouds, or fog, or dew, or other atmospheric variations, should
be especially noted.

V. DRAWINGS OF THE CORONA.

Careful drawings of the corona may be of value. The ob-
server should provide himself with a tablet to draw upon, and
a couple of soft pencils (No. 2, or BB), sharpened at both ends.
In the middle of the paper draw two lines at right angles, and
mark their extremities top, bottom, right, left. With their inter-
section as a centre and a radius of one inch draw a circle to
represent the moon. During totality fill in the details deliber-
ately and conscientiously. A careful drawing half finished is
better than one covering all the region which is done in haste.
Send the original drawing with notes to the Lick Observatory
for comparison with others of the same kind.

A really important observation can be made in the follow-
ing way: Place a circle of wood, or iron, 12 inches in diame-
ter, near the top of a telegraph or other pole, and place the
eye at about 57 feet from the disc, so that at the time of total-
ity the center of the disc will cover the center of the sun.
The position for the eye can be approximately determined on
the days immediately preceding the eclipse, and a stake can
be firmly driven, over the very top of which the observer is to

The Eclipse of January 1, . 1889. IB

look at the totally eclipsed sun. The sun, and the inner (and
brighter) corona will be hidden, and the eye can then follow
the outer and fainter portions with ease, and estimate their
directions (angles with the vertical post) and their lengths (in
diameters of the disc). The eye should be kept in darkness
up to the beginning of the total phase.

VI. SPECIAL PHENOMENA.

(Near the times of beginning and end of the eclipse.)

(i). Visibility of the limb of the moon before it touches
and after it leaves the sun, and the time and distance at which
it is noticed.

(2). Apparent agitation of the sun's limb near the point of
contact immediately before and after the eclipse.

(3). Whether the contacts are instantaneous and well de-
fined, or whether there are apparent adhesions and distortions,
formation of beads, or portions of the moon's limb separated
by dark lines, or other irregularities of outline.

(During the progress of the eclipse.)

(4). Projection of the moon beyond the sun; the time and
extent to be noted.

(5). Irregularities of the moon's limb. Distortions of the
solar cusps, their color, and shading.

(7). Bright band bordering the the moon's edge; color of
the glass screen through which the moon is best seen.

(8). Flashes or coruscations of light across the moon.

(9). Any peculiarities in the illumination and color of the
moon's disc or any portion of it ; spots which may be visible.

(10). Any peculiarity in the appearance and color of the
solar spots, especially near the edge of the moon.

(Near the instants of total immersion and of emersion.)

(11). Rapid change of the last visible portion of the sun, or
of that which first reappears; a separation into minute parts,
or formation of Baily's beads, with dark lines among them.

16 Suggestions for Observing

(12). Any increased brightness of the moon's edge, and when
and where it is noticed.

(13). Flashes, rays, or bright points as the sun disappears or
reappears.

(14). The approach and recession of the shadow, appearing
on the ground like that of a cloud, should be watched by those
who are not occupied with other observations; and any pecu-
liarities described, as for instance, whether its appearance and
motion are uniform, or if dark stripes appear flitting across
the landscape; if these are seen their distance apart, width,
and velocity should be noted.

(During the total phase.)

(15). The general appearance and extent of the corona;
when and where it first appears and disappears; whether uni-
formly surrounding the moon's disc, or brighter and more
extensive on one side, especially where the sun has just disap-
peared, or is about reappearing; its color in different portions;
its shading, and whether separated into two portions, one
brighter and shaded uniformly, the other radially striated; its
changes.

(16). Prominences or protuberances along the edge of the
moon, with their position, form, extent, color, and any other
peculiarity; also their formation, growth, and any other changes.
The position and extent should be noted on a diagram pre-
viously prepared.

(17). Colors of the clouds or fog, and especially a note of
the changes of color.

If there are several observers with telescopes, it is desirable
that one should keep the whole corona in view, while each of
the others confines his attention to some designated portion.
Those without telescopes, or supplied with opera-glasses, or
spy-glasses, should also note the appearance, extent, and pecu-
liarities of the corona, as it appears to them.

(18). A comet may possibly be seen near the sun, or an
aurora be visible.

The Eclipse of January 1, 1889. 17

VII. PHOTOGRAPHY.

Photographs of the corona of very considerable scientific
value can be made with the apparatus in ordinary use by photo-
graphers. With this view, the camera should be fitted with the
largest and longest focused lens at the operator's disposal, and
then should be most carefully focused with the full aperture,
upon some distant object placed in the middle of the ground
glass. The image will be well defined over a small space in
the center of the ground glass only, but that is of no conse-
quence, Two or three minutes before totality, six or eight
plates should be in readiness for immediate use. The camera
should also be in readiness, directed towards the sun, and held
there in any convenient manner. As the sun will be at a con-
siderable altitude, the ordinary camera stand may not be avail-
able, but with a little ingenuity some rough contrivance can be
made which will answer the purpose.

The camera should be carefully examined beforehand to see
if it is light-tight, by covering the head with a heavy, thick
black cloth, and looking into the camera from the rear with
the lens in place and cap on, and also from the front with the
plate-holder in place and the lens-front removed. This should
be done in strong sunlight, and the camera turned in every
direction, to detect any pin-holes in the bellows, or cracks and
leaks in the woodwork, and especially in the fitting of the
plate-holder and the sliding front. Very few new cameras, and
still fewer old ones, are absolutely light-tight, and the smallest
quantity of outside light, admitted in this way, will greatly in-
jure or entirely destroy what might otherwise be a perfect neg-
ative.

All the holders should be filled and laid beside the camera,
so that they can be used without delay. Then, the focus of
the camera remaining as it was when adjusted upon the distant
object, so soon as totality commences and the operator has
assured himself that the image of the corona is in the center
2

18% Suggestions for Observing

of the ground glass, he should insert a plate, and expose it.
The ground glass should next be replaced, when, owing to the
diurnal motion of the earth, it will be seen that the image of
the corona has moved away from the center of the field. It
should then be put back, after which another plate should be
inserted and exposed; and this routine should be repeated till
the totality is over, when the plates can be developed.

If the camera is provided with any one of the simple finders
which are used in taking instantaneous views, it will not be
necessary to examine the ground glass after each exposure,
and the number of exposures can be materially increased.
If the image of the sun is in the center of the field of the
finder, it must be in the proper place on the plate. With a
little previous attention to sighting the camera, by looking
along the corners, or the middle of the upper side, any given
object can be placed sufficiently near the center of the plate.
This will be more easily done with simple sights attached to
the camera, and adjusted to point at a distant object when it
is in the middle of the plate.

It seems to be preferable not to give definite directions for
the exposure-times with each lens and plate likely to be used,
but rather to suggest a general plan of work and to leave the
details to the individual operator.

Valuable experience can be had by photographing light
clouds away from the sun ; or near the sun, when it is obscured
by heavy clouds; or just after sunset. Several exposures of
different times made in this way will show which one is best
suited to give all the details of the cloud forms, and this
exposure (and stop) is the one best suited for photographs of
the corona. With the full aperture of a portrait-lens, the max-
imum time should probably not exceed five seconds. Some of
the exposures should be shorter, down to the quickest, which
can be made with the cap (something near half a second).
One plate should be exposed with the smallest stop and the
shortest time with the cap; another with the same time and an
intermediate stop. By thus varying the amount of light re-

The Eclipse of January 1, 1859. 19

ceived by the plates, there is more likelihood of obtaining a
successful picture, showing the delicate details of the corona.

The photographer should make the preliminary experiments
here recommended, and settle on a programme which he will
follow on the day of the eclipse. This programme should
indicate the times of exposure and the various stops to be
employed, and should be strictly observed if the day of the
eclipse is clear. If the day is foggy or overcast, a new pro-
gramme can be made. In any event the data named should
be known for each plate exposed.

Every possible care should be used to avoid fogging the
plates in placing them in the holders, and in removing them
after exposure, as well as in the earlier stages of development.
Only a feeble red light should be used, not yellow or orange-
green. An amount of fogging which would be imperceptible
in a portrait negative will utterly spoil what might otherwise
have been a satisfactory negative of the corona. The camera
must be covered with a black cloth whenever the slide is drawn,
as a matter of course.

Only one plate at a time should be developed, and the
development should be carried on very slowly and cautiously
to determine whether the plates have been over- or under-
exposed. Each plate should be fixed and examined before
the development of another is commenced, so that the propor-
tions of the developer may be intelligently varied, if necessary.
In any case the development should not be hurried. To get
the best results, it may be desirable to spend half an hour and
upwards on each plate. With a short time and a strong devel-
oper, many of the more delicate details of the corona are cer-
tain to be lost.

On account of the motion of the earth while the plate is
being exposed, the image of the sun — or rather of the moon,
which covers the sun — will be a little blurred, and somewhat
oval in shape; and to prevent disappointment, it must be borne
in mind that the portrait lenses in ordinary use have such short
foci that they can give but very small pictures of the moon.

20 Suggestions for Ob se ruing1

The actual size in inches will be nearly as follows, viz.: With
a 1-4 lens (focus about 5 inches), 0.04 inches; with a 1-2 lens
(focus about 8 inches), 0.07; with a 4-4 lens (focus about 10
inches), 0.09; and with an extra 4-4 lens (focus about 1 6 inches),
0.14. The diameter of the extreme outlying portions of the
corona may be four or five times these figures.

It is hoped that photographers making pictures in this man-
ner will send the original negatives to the Lick Observatory;
but if they prefer to retain them, it is earnestly requested that
they will, at least, send positive copies on glass. Paper prints
are useless for scientific purposes.

Each plate should be accompanied by a statement of the
kind of lens used in its production; the focal distance and
aperture of that lens; the diaphragm employed; the kind of
plates used ; how long each plate was exposed ; and the means
of identifying the top. The latter point is of especial impor-
tance, and the upper side of every plate must be carefully
marked when it is put in the holder, because the character of
the corona is such that without this precaution it may be impos-
sible to say certainly which is the top of the negative.

Any dry-plate, with which the photographer is acquainted,
may be used, but preference should be given, other things being
equal, to plates giving a good degree of intensity and con-
trast in the images. The Seed plate (Sensitometer Nos. 22 to
26) is specially well adapted to this work. The quick Passa-
vant plates are also suitable. Of course the rapidity of the
plate will be taken into account in giving the exposure.

It is desirable, though by no means essential, that every
photographic observer should be provided with an assistant to
record for him. The record should be made in pencil, on
pieces of white cardboard, cut to a convenient size. Each
observer should be provided with colored or smoked glass to
view the sun during the partial phase, so that he may not be
dazzled, and lose precious time when the totality comes on.

A couple of photographs of the sky, taken just before and
again after totality, will be interesting to show the position
and motion of the clouds. For these negatives the smallest

The Eclipse of January 1, 1889. 21

stop should be used, and the time made as short as possible,
preferably with an instantaneous shutter.

Plate-holders of the form that fit on the camera back from
behind and catch, rather than the sliding kind, are the best, as
they can be more quickly attached, and as this can be done
with less danger of moving the instrument. The time required
to insert this form of holder, draw the slides, push them back
again, remove the holder, and pick up another one, may be
taken as twelve seconds, or six seconds to a plate. It can be
done in eight seconds, or even less, but it is better to take more
time and avoid jarring the camera, or setting it in vibration.
Twelve seconds is ample time for an 8 by 10 holder, and no
further time allowance need be made. The slide should be
drawn as far as a chalk mark previously placed upon it, and
then pushed back, instead of removing it entirely as usual, the
camera being covered with a dark cloth. By this means a full
second and a half may be saved. Of course the projecting
slide must be protected from the wind. If it is intended to
use a diaphragm with any one of the series of plates, it is
better to take this plate after the other more important expos-
ures have been made without diaphragms.

When great accuracy is not necessary, the simplest way to
orient the pictures is to take a couple of instantaneous views
of the sun fifteen or twenty minutes before totality, and about
one minute apart, upon the same plate (the driving clock of
the telescope being stopped in the meantime, if the camera is
mounted on a telescope stand). Take two more about the
same interval after totality. The mean direction of motion of
the cusps on these two plates should give the direction of the
circle of declination during totality, within ten or fifteen
minutes of arc.

The plates should be numbered with a soft pencil on the
corner of the film before removing them from the plate-holder.
The intended exposure for each plate should be indicated in
large white letters on the slide. The black tablet slides are
very convenient for this purpose, as the figures may be chalked
directly upon them.

Photomount

Pamphlet

Binder

Gaylord Bros., Ii

Makers
Stockton, Call

PAT. JAN. 21. 1908

>ugges
e TO
sun on

.ons for observ
se of ti
Janikary'l, 1889

851037

4 81

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